Solid surface lubricant coating

ABSTRACT

Metal articles are provided with a heat resistant, wear and abrasion resistant, antiseizing, solid surface lubricant coating consisting essentially of the combination of silver and niobium di-telluride.

Elite States patent odshire et ai.

SOLID SURFACE LUBRICANT COATING [73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Mar. 24, 1972 [21] Appl. No.: 237,950

[52] U.S. Cl. 29/195 Y, 252/12 [51] Int. Cl ClOm 7/00 [58] Field of Search 29/195 Y; 252/12,

[56] References Cited UNITED STATES PATENTS 3,405,063 10/1968 Boes et a1. I. 252/12 Jan. 15, I974 Primary Examiner-L. Dewayne Rutledge Assistant ExaminerE. L. Weise Attorney-Sidney Carter et a1.

[57] ABSTRACT Metal articles are provided with a heat resistant, wear and abrasion resistant, antiseizing, solid surface lubricant coating consisting essentially of the combination of silver and niobium di-telluride.

6 Claims, No Drawings SOLID SURFACE LUBRICANT COATING The invention herein described was made in the course of work under a contract or subcontract thereunder with the United States Air Force.

This invention relates to solid surface lubricant coatings for metal articles and, more particularly, to an improved heat resistant, wear and abrasion resistant, antiseizing, solid surface lubricant coating.

Wear surfaces of metal gears, splines, screws and bolts are often subject to wear, abrasion, seizing and fretting when contacting and moving against other metal surfaces, particularly under oil starvation conditions. This problem is known to be particularly acute at elevated temperatures, such as those encountered in gas turbine engine applications, where conventional wet and dry surface lubricants deteriorate. Therefore, there is a need for an improved surface lubricant coating which is wear and abrasion resistant, has antiseizing properties and low shear properties to reduce fretting,

at least the wear surfaces of metal articles with an improved solid surface lubricant coating which is stable at temperatures up to about l,500 F including the combination of silver and niobium di-telluride in suitable proportions to improve the antiwear characteristics of the article and to provide lubricity under conditions of oil starvation.

In general, these and other objects are accomplished by applying by an electrophoretic process a powdered mixture containing silver and niobium di-telluride as a layer over at least the wear surfaces of the metal article to a thickness of at least about 0.0005 inch to form an adherent coating which affords the wear surfaces with outstanding wear resistance and lubricity. Preferably, the proportions of silver and niobium di-telluride in the mixture are such that the proportion of silver in the coating is about 60-73 percent, by weight, with the balance niobium di-telluride.

The solid surface lubricant coating comprising this invention is compatable with any metal or alloy. However, as indicated above, one of the advantages of the coating is its stability at elevated temperatures up to about l,500 F. Accordingly, this invention is concerned primarily with articles of manufacture formed of heat-resistant or refractory metals and alloys commonly used for elevated temperature applications. Refractory metals and alloys include molybdenum, columbium, tungsten, tantalum, titanium and alloys thereof. Heat-resisting alloys include generally low carbon-chromium-molybdenum alloy steels with up to about percent alloying, ferritic and martensitic and austenitic stainless steels containing 12-27 percent chromium, higher-nickel austenitic steels contining 25-40 percent nickel, precipitation hardening stainless steels such as 17-4 PI-I which has a nominal composition of, by weight, 16.5 percent chromium, 4.25 percent nickel, 3.6 percent copper and 0.25 percent columbium, iron-chromium alloys containing from 10-30 percent chromium and little or no nickel, ironchromium-nickel alloys containing more than 18 percent chromium and more than 7 percent nickel, ironnickel-chromium alloys containing more than 25 percent nickel and 10 percent chromium, cobaltchromium-nickel alloys, nickel-based superalloys containing 40-80 percent, .by weight, nickel, 5-20 percent chromium, and the balance other constituents; and cobalt-based superalloys containing 45-70 percent cobalt, 15-30 percent chromium, and the balance other constituents. In the case of the nickel-based alloys, the other constituents may include up to 10 percent molybdenum, up to 5.5 percent titanium, up to 6.5 percent aluminum, up to 3 percent columbium, up to 9 percent tantalum, up to 13.5 percent tungsten, up to 2 percent hafnium, up to 1 percent rhenium, up to 1.5 percent vanadium, up to 20 percent. cobalt, up to 3 percent iron, and minor amounts of cesium, boron, zirconium, silicon, manganese, and impurities in the form of sulphur, copper and phosphorus. In the case of cobalt-based alloys, the other constituents may include up to 7 percent molybdenum, up to 10 percent tantalum, up to 16 percent tungsten, up to 16 percent nickel, up to 3 percent iron, minor amounts of carbon, manganese, silicon, titanium, boron, zirconium, and impurities in the form of iron, sulphur, phosphorus and copper.

Other objects and advantages will be apparent from the following detailed description of the invention. For purposes of description, the invention will be set forth in terms of the method of applying the coating.

The silver-niobium di-telluride coating is applied to metal articles or at least the wear surfaces thereof by an electrophoretic method. In general, this method consists of applying a particulate coating of silver and niobium di-telluride to the article by suspending metal particles of suitable particle size in an organic dielectric solvent and impressing a direct current of about 200 volts between two electrodes, thus causing the metallic particles to uniformly deposit on the article, which is one of the electrodes, and adhere thereto.

A preferred coating bath consists of a solution of 55-65 percent, by weight, isopropanol and 35-45 percent, by weight, nitromethane to which is added 15 to 20 grams per liter silver metal powder having a particle size of 0.5 to 1.5 microns, 7.5 to 10 grams per liter niobium di-telluride powder having a maximum particle size of 5 microns, and 1.5 to 3.5 grams per liter cobalt nitrate-prolamine protein.

The article to be coated may, if desired, be first cleaned by vapor degreasing or solvent techniques or by dry honing, using number 260 grit or finer aluminum oxide abrasive. The article is then immersed in the bath and made anodic. A voltage of about 200 volts is applied across the electrodes for about 5 seconds, whereby the powdered metals are caused to migrate to and be deposited uniformly over the article surface. Sufficient amounts of the cobalt nitrate-protein complex is also deposited along with the powders to act as a binder. The composition of the coating thus applied is directly proportional to the concentration of the dispersed metal particles in the bath. Accordingly, the coating consists of, by weight, about 60-73 percent silver and the balance niobium di-telluride with about 67% silver, by weight, being preferred. Preferably, the thickness of the coating is at least 0.0005 inch to insure coextensive coating of the wear surfaces. We prefer that the thickness be less than 0.002 inch, however,

thicker coatings may be applied but without advantage.

Articles so coated have been found to exhibit excellent wear and abrasion resistance,-antiseizing and antifretting properties, a relatively low static coefficient of friction, and stability at temperatures up to about l,500 F.

Thus having described our invention, what is claimed 1. An article of manufacture comprising a metal base and an adherent, abrasion resistant, solid surface lubricant coating of a thickness of at least about 0.0005 inch on at least a portion of said base, said coating consisting essentially of the combination of about 60 to 73 percent, by weight, silver and the balance niobium ditelluride.

2. An article of manufacture according to claim 1 wherein said coating consists essentially of about 67 percent, by weight, silver and the balance niobium ditelluride. I

3. An article of manufacture comprising a metal base and an adherent, abrasion resistant, solid surface lubricant coating of a thickness in the range of about 0.0005 to 0.002 inch on at least a portion of said base, said coating consisting essentially of the combination of about60 to 73 percent, by weight, silver and the balance niobium di-telluride.

4. An article of manufacture comprising a base formed of an alloy chosen from the group consisting of refractory and heat-resistant alloys and an adherent, abrasion resistant, solid surface lubricant coating of a thickness of at least about 0.0005 inch on at least a portion of said base, said coating consisting essentially ofthe combination of about 60 to 73 percent, by weight, silver and the balance niobium di-telluride.

5. An article of manufacture comprising a base formed of an alloy chosen from the group consisting of refractory and heat-resistant alloys and an adherent, abrasion resistant, solid surface lubricant coating of a thickness in the range of about 0.0005 to 0.002 inch on at least a portion of said base, said coating consisting essentially of the combination of about 60 to 73 percent, by weight, silver and the balance niobium ditelluride.

6. An article of manufacture according to claim 5 wherein said coating consists essentially of about 67 percent, by weight, silver and the balance niobium ditelluride. 

2. An article of manufacture according to claim 1 wherein said coating consists essentially of about 67 percent, by weight, silver and the balance niobium di-telluride.
 3. An article of manufacture comprising a metal base and an adherent, abrasion resistant, solid surface lubricant coating of a thickness in the range of about 0.0005 to 0.002 inch on at least a portion of said base, said coating consisting essentially of the combination of about 60 to 73 percent, by weight, silver and the balance niobium di-telluride.
 4. An article of manufacture comprising a base formed of an alloy chosen from the group consisting of refractory and heat-resistant alloys and an adherent, abrasion resistant, solid surface lubricant coating of a thickness of at least about 0.0005 inch on at least a portion of said base, said coating consisting essentially of the combination of about 60 to 73 percent, by weight, silver and the balance niobium di-telluride.
 5. An article of manufacture comprising a base formed of an alloy chosen from the group consisting of refractory and heat-resistant alloys and an adherent, abrasion resistant, solid surface lubricant coating of a thickness in the range of about 0.0005 to 0.002 inch on at least a portion of said base, said coating consisting essentially of the combination of about 60 to 73 percent, by weight, silver and the balance niobium di-telluride.
 6. An article of manufacture according to claim 5 wherein said coating consists essentially of about 67 percent, by weight, silver and the balance niobium di-telluride. 